I use 2 sheets of "dirty Board" or some call it black board. This is the stuff they used to put on the houses as sub siding. You will need to buy 2 sheet and just double them up one on top of the other. I now have a very nice building table that is 4x8. It is very cheap and beleive it or not, the local lumber companies still stock it. I cover it with a roll of white paper from the local paper mill. It was the end scrap peices. It was also free. The dirty board is very easy to get the pins in and the pins hold very tight.
Just my 2 cents!
Don